This invention relates in general to the precise adjustment or "conditioning" of integrated circuit device leads and, more specifically, to a method and apparatus for adjusting the leads sequentially for lead standoff, lead spread, lead sweep and coplaarity.
Various electronic devices, such as integrated circuits and memory devices are mounted in flat plastic or ceramic packages with rows of J-shaped input/output electrical leads extending upwardly above the device surface around two or four edges. The devices are typically surface mounted on solder lands with system leads brought into contact with the device leads or the device leads are inserted into corresponding sockets. The device leads must be precisely located and positioned relative to each other and to the device so that proper electrical contact can be made with system leads. Often during manufacture of the devices or handling after manufacture the leads can be bent out of alignment. For example, the lead standoff, the distance the leads extend above the device upper surface, may vary, making uniform contact with the leads difficult. Also, the lead spread between the upward leg of the leads and the edge of the device may vary and the distance between adjacent leads, lead sweep, may vary.
Attempts have been made to design tools and apparatus for conditioning the leads to correct various misalignments. Prior devices generally are capable of straightening straight leads, such as terminal pins arrayed in rows and columns across a support. Typical of these are the devices is that disclosed by Camp in U.S. Pat. No. 4,371,013, where a straightening bar having one or a plurality of spaced holes or apertures with tapered entrances are lowered over terminal pins to bend them back to a desired straightness and parallel alignment. Similarly, Kent in U.S. Pat. No. 4,397,341 provides a device for straightening terminal pins which includes a plurality of parallel bars having rows of apertures. A support having a plurality of terminal pins in rows and columns is moved toward the aligned bars so that the pins enter the apertures. Alternate bars are reciprocated short distances in opposite directions to flex the pins and align them in a precisely parallel array. While effective with terminal pin arays, these devices are not suitable for aligning curved pins and can only straighten and assure parallelity of straight pins. They are incapable of conditioning the other characteristics mentioned above, such as lead standoff, lead spread and lead sweep.
Other lead conditioning devices have been designed to accommodate rows of leads exiting the edges of electronic components and bent to extend beyond one face of the component. Typical of these are the devices described by Linker in U.S. Pat. No. 4,481,984 and by Liner et al. in U.S. Pat. No. 3,880,205. These devices, however, can only accommodate rows of pins on two opposite sides of a electronic component base, since each passes the components along a trackway having spreader to bend the pins outwardly beyond the desired angle, and simultaneously or subsequently uses a comb-like device to straighten and align the leads in parallel. While effective with some types of leads, such as straight or "banjo" type leads, these devices are not capable of properly configuring curved leads requiring conditioning of lead standoff, spread, sweep, etc.
Thus, there is a continuing need for improved methods, tools and apparatus for rapidly and accurately conditioning the leads on multi-lead electronic devices such as PLCC and other packages using J-shaped leads.